1. Field of the Invention
The present invention generally relates to a starter used for starting an internal combustion engine.
2. Related Art
According to the Japanese Patent Laid-open Publication No. 61-105761, a movable contact that directly contacts a fixed contact fixed in an end frame that covers one end of a motor chassis is set in the motor chassis. A copper strand wire is wound on one end of the movable contact with a nut, and the other end of the copper strand wire is directly connected to the input end portion of a field coil together with the output side lead wire of a solenoid coil.
Furthermore, an attraction coil that attracts when energized, and a plunger set on the inner circumference of this attraction coil are set in the switch. A rod is connected to one end of this plunger, and a shift lever to slide an overrunning clutch is connected to the other end. A lever is fixed to the rear end of the rod with a snap ring, and this lever is inserted into the motor chassis. A movable contact is wound onto the insertion end portion with a nut. Furthermore, the lever is covered with a rubber cover.
In such a starter, when the attraction coil is energized, the plunger is attracted by the electromotive force of the attraction coil and the movable contact fixed to the lever moves with the plunger to contact the fixed contact fixed on the end frame. Thus the battery voltage is then applied on the field coil via the copper strand wire connected to the movable contact, the armature is energized via the brush and commutator thereby drives the starter.
However, when the engine is started with the conventional starter, a large current flows to the armature causing the starter to rapidly heat up. The heat generated on the portion where the commutator and brush contact becomes the highest. The heat is dissipated through the brush, field coil, copper strand wire, movable contact, fixed contact to the battery cable, and thus, the dissipation path is extremely large. Furthermore as there is the field coil that acts as the field magnetic pole in the dissipation path, the brush is not sufficiently cooled, and may cause the brush life to drop.